Guide blade segment of a gas turbine and method for its production

ABSTRACT

A guide blade segment of a gas turbine, having at least one guide blade and having an inner cover band assigned to the radially inner end of the or each guide blade, is disclosed. An integral constituent part of the inner cover band of the guide blade segment is a sealing element, which serves to seal a radially inner gap between the guide blade segment and a gas turbine rotor.

This application claims the priority of International Application No. PCT/DE2007/000097, filed Jan. 19, 2007, and German Patent Document No. 10 2006 004 090.2, filed Jan. 28, 2006, the disclosures of which are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a guide blade segment of a gas turbine. In addition, the invention relates to a method for producing a guide blade segment of a gas turbine.

Gas turbines, particularly gas turbine aircraft engines, have stationary guide blade rings and rotating rotor blade rings in the region of their compressors and turbines, wherein the stationary guide blade rings are assigned to a stationary housing and the rotating rotor blade rings to a rotating rotor of the gas turbine. The stationary guide blade rings are formed by several guide blade segments, wherein each guide blade segment includes at least one guide blade. Assigned to the radially inner end of the or each guide blade of a guide blade segment is an inner cover band, wherein, in order to guarantee an optimal degree of efficiency of a gas turbine, a radially inner gap between the inner cover band of the guide blades and the rotor of the gas turbine needs to be sealed. Sealing the radial inner gap between the inner cover band and the rotor of the gas turbine is accomplished using what is commonly called an inner air seal, wherein, for this purpose, sealing elements are assigned to the inner band of the guide blade segments. These sealing elements can be designed as honeycomb seals.

In the case of guide blade segments known from practice, the sealing elements are designed as separate components and are permanently connected to the inner cover band of the guide blade segments by soldering for example. The result of this is a high manufacturing effort, since, on the one hand, the sealing elements must be manufactured as a separate component using separate manufacturing methods, and since, on the other hand, the sealing elements have to be connected to the inner cover band using a joining method. Furthermore, soldered connections for the most part represent thermo-mechanical weak points.

Starting herefrom, the present invention is based on the objective of creating a novel guide blade segment of a gas turbine and a method for producing same. According to the invention, an integral constituent part of the inner cover band of the guide blade segment is a sealing element, which serves to seal a radially inner gap between the guide blade segment and a gas turbine rotor.

In terms of the present invention, it is provided in the case of a guide blade segment of a gas turbine, that the sealing element be designed as an integral constituent part of the inner cover band of the guide blade segment. This is preferably accomplished in that the sealing element and the inner cover band of the guide blade segment are manufactured integrally in a forming process. Manufacturing costs can be reduced due to the integral design of the sealing element with the inner cover band of the guide blade segment, because, on the one hand, a separate manufacturing process for the sealing element and, on the other hand, a joining of the sealing element to the inner cover band of the guide blade segment are eliminated. By eliminating joined connections between the sealing element and the inner cover band of the guide blade segment, the service life of the guide blade segments can also be increased, because the joined connections or joined points that are required by the prior art between the sealing element and the inner cover band of the guide blade segment represent weak points. In particular, eliminating the soldering heat treatment that is customary in the case of compressor guide blade segments does not reduce the fatigue strength of the guide blade segments.

Preferred developments of the invention are disclosed in the subsequent description. Without being limited hereto, exemplary embodiments of the invention are explained in greater detail on the basis of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic section of an inventive guide blade segment of a gas turbine in the region of an inner cover band of the guide blade segment; and

FIG. 2 is a detail of the inner cover band from FIG. 1 in the region of a sealing element embodied as an integral constituent part of the inner cover band.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section of an inventive guide blade segment of a gas turbine in the region of an inner cover band 10 arranged on radially inner ends of guide blades of the guide blade segment, wherein a sealing element 11 is assigned to the inner cover band 10 in the exemplary embodiment in FIG. 1. The sealing element 11 serves to seal a radially inner gap between the guide blade segment and a gas turbine rotor.

In terms of the present invention, the sealing element 11 is an integral constituent part of the inner cover band 10 of the guide blade segment. The sealing element 11 in this case is either integrally cast on the inner cover band 10 of the guide blade segment or integrally formed on the inner cover band 10 using powder metallurgical injection molding. The sealing element according to FIG. 2 is preferably embodied as a honeycomb seal made of several honeycombs 12, wherein the honeycombs 12 can have any contour. Thus, FIG. 2 exemplarily shows honeycombs 12, which have a round contour in cross section, as well as honeycombs 12, which have a hexagonal or honeycombed contour in cross section.

As already stated above, the inventive guide blade segment is preferably manufactured in that the sealing element is either integrally cast on the inner cover band, integrally formed on the inner cover band using powder metallurgical injection molding, or the sealing element and the inner cover band are integrally manufactured using generative manufacturing methods.

If the manufacturing variant of powder metallurgical injection molding, which is also known as the metal injection molding (MIM) method, is selected, the preferred procedure is that a common molded article is manufactured by injection molding for the inner cover band and thus the guide blade segment as well as the sealing element, wherein the molded article is also designated as a green compact. In this case, the sealing element is then already an integral constituent part of the inner cover band in the green compact, wherein subsequently, as is customary in powder metallurgical injection molding, a binding agent and plasticizing agent are expelled from the green compact to produce a brown compact. The brown compact is then sintered in order to make the guide blade segment available.

Alternatively, it is also possible to manufacture separate green compacts for the inner cover band or the guide blade segment and the sealing element, wherein brown compacts are manufactured from these green compacts by expelling the binding agent and plasticizing agent, and the brown compacts are then formed on one another and jointly sintered.

A further alternative for powder metallurgical injection molding can be seen in first manufacturing a green compact for the inner cover band or guide blade segment and converting this green compact into a brown compact by expelling the binding agent and plasticizing agent, wherein the sealing element is then integrally formed on this brown compact by injection molding.

In powder metallurgical injection molding, the composition of a homogeneous mass made of metal powder, binding agent, and plasticizing agent that is used for injection molding can be adapted. Thus, when a common molded article or green compact is manufactured by injection molding for the inner cover band and the sealing element, during injection molding, the composition of the homogenous mass used for injection molding can be modified in order to thereby guarantee different properties in the region of the sealing element than in the rest of the guide blade segment.

Instead of the one-component injection molding, a two-component injection molding can also be carried out, wherein a first homogenous mass is then used for the injection molding of the guide blade segment, and a second homogeneous mass is used for the injection molding of the sealing element, and these two homogenous masses differ in terms of their compositions. The compositions are adapted respectively to the required properties of the guide blade segment and sealing element.

A hard metal powder and/or a powder of intermetallic phases, such as, e.g., titanium aluminide, and/or a powder of metal alloys can be used as the metal powder in the respective, homogeneous mass required for injection molding. In addition or as an alternative to the metal powder, a ceramic powder can also be used as the homogeneous mass required for injection molding.

In the case of the alternative manufacturing route using generative manufacturing methods, the sealing element and the inner cover band are built up in layers integrally, i.e., made of one piece, in particular using rapid prototyping methods. Used preferably as the generative manufacturing method is laser engineered net shaping, which uses electron-beam melting, laser sintering, laser melting, laser shaping, or laser powder application welding. Cobalt, nickel, iron, or even titanium-based alloys can be used for this, in that as sinterable powders, these materials are built up in layers by means of a source of radiation in a natural or artificial environment directly from the component's CAD data.

Due to this layered structure, solid and even hollow structures can be manufactured in a manner that is satisfactory in terms of load. The sealing element can consequently be structured in a simple manner as a hollow space that is open on one side (e.g., honeycombs), as a metallic grid structure, or a foam structure.

Following the different manufacturing routes, finish machining for the final contour can also still be performed by removal methods such as milling, lathing, eroding, or electrochemical processing. 

1-13. (canceled)
 14. A guide blade segment of a gas turbine, comprising a guide blade and having an inner cover band assigned to a radially inner end of the guide blade, wherein an integral constituent part of the inner cover band of the guide blade segment is a sealing element, which seals a radially inner gap between the guide blade segment and a gas turbine rotor.
 15. The guide blade segment according to claim 14, wherein the sealing element is integrally cast on the inner cover band.
 16. The guide blade segment according to claim 14, wherein the sealing element is integrally formed on the inner cover band using injection molding.
 17. The guide blade segment according to claim 14, wherein the sealing element is a honeycomb seal.
 18. A method for producing a guide blade segment of a gas turbine, wherein the guide blade segment has a guide blade and an inner cover band assigned to a radially inner end of the guide blade, wherein a sealing element, which seals a radially inner gap between the guide blade segment and a gas turbine rotor, is formed on the inner cover band of the guide blade segment as an integral constituent part of the inner cover band.
 19. The method according to claim 18, wherein the sealing element is integrally cast on the inner cover band.
 20. The method according to claim 18, wherein the sealing element is integrally formed on the inner cover band using injection molding.
 21. The method according to claim 20, wherein a common molded article or a green compact is produced during the injection molding for the sealing element and the inner cover band.
 22. The method according to claim 20, wherein separate molded articles or green compacts are produced during the injection molding for the sealing element and the inner cover band, which as brown compacts are formed on one another and jointly sintered.
 23. The method according to claim 20, wherein the injection molding is carried out as two-component injection molding.
 24. The method according to claim 20, wherein a homogeneous mass made of a powder, a binding agent, and a plasticizing agent is used during the injection molding and wherein a hard metal powder and/or a powder of an intermetallic phase and/or a powder of metal alloys and/or a ceramic powder is used as the powder.
 25. The method according to claim 18, wherein the sealing element and the inner cover band are integrally formed by a generative manufacturing method.
 26. The method according to claim 25, wherein the generative manufacturing method is a rapid prototyping method.
 27. The method according to claim 25, wherein the generative manufacturing method is laser engineered net shaping, electron-beam melting, laser sintering, laser melting, laser shaping, or laser powder application welding.
 28. A method for producing a guide blade segment of a gas turbine, wherein the guide blade segment has a guide blade and an inner cover band on a radially inner end of the guide blade, comprising the step of: integrally forming a sealing element on the inner cover band of the guide blade segment.
 29. The method according to claim 28, wherein the step of integrally forming the sealing element on the inner cover band of the guide blade segment includes integrally casting the sealing element on the inner cover band.
 30. The method according to claim 28, wherein the step of integrally forming the sealing element on the inner cover band of the guide blade segment includes injection molding.
 31. The method according to claim 28, wherein the step of integrally forming the sealing element on the inner cover band of the guide blade segment includes a generative manufacturing method.
 32. The method according to claim 31, wherein the generative manufacturing method is a rapid prototyping method.
 33. The method according to claim 31, wherein the generative manufacturing method is laser engineered net shaping, electron-beam melting, laser sintering, laser melting, laser shaping, or laser powder application welding. 